The present disclosure generally relates to three-dimensional road maps, and more specifically to determining a three-dimensional road map given relative orderings at intersections, and potentially providing the three dimensional road map to a navigation device for displaying road views.
A device featuring global positioning system (GPS) navigation typically receives GPS signals to determine the current location of the device. A GPS navigation system may display the location of the device relative to a road depicted in a map image to aid in navigation. For example, a navigation system may show an icon representing a vehicle in which the device is located relative to an image of a road within a map. As the device travels along a road toward an intersection (an example of a junction), the navigation system may show the icon gradually advancing toward an intersection shown in the map image. In some cases, a road of an intersection may pass over another road of the intersection. Because the navigation application displays a two-dimensional image of the intersection, it may not be possible for the driver to determine from the displayed image that a road passes over another road. And, even if the navigation device did know an ordering of the height of the roads, the image would be disorienting (e.g., the image might just show one road disappearing) since no height information leading up to an overpass (another example of a junction) is available.
Additionally, since such devices only receive two-dimensional information, the user has no sensory cues about the terrain he/she will travel on or is currently traveling on, at least not from the navigation device. Given the flat two-dimensional views, or even projecting the two-dimensional view onto a three-dimensional scene, providing directions via such navigational devices can be confusing. However, determining three-dimensional images of a road map is not straightforward unless one measures road heights or gradients, which would be very expensive.
Therefore, it is desirable to provide plausible three-dimensional road maps using existing two-dimensional road map information with simple stacking information at junctions.